A sensitive spectrofluorimetric method was developed for the determination of famciclovir in pure and pharmaceutical preparations. The method is based on the derivatization reaction of famciclovir with fluorescamine. The different experimental parameters that affect the fluorescence intensity were carefully studied, at once. The method was validated for linearity, limit of detection, limit of quantification, precision, accuracy, recovery, robustness. The assay was linear over the concentration range of 100 and 1000 ng/mL. The limits of detection and limit of quantification were calculated to be 51.13 and 153.39 ng/mL. The proposed method was applied to study of famciclovir in pure and in pharmaceutical preparations.